The invention relates to a method for compensating torsional vibrations of a printing machine by introducing torques which compensate the vibration excitation. The invention relates, furthermore, to apparatus for performing this method, with at least one device for introducing torques into the drive train of a printing machine for compensating vibration excitations.
Various types of vibrations occur in printing machines and influence print quality. Predominent originating sources of vibrations are cylinder channels or gaps and also sheet transfer elements and other discontinuously operating machine elements. This leads, on the one hand, to bending vibrations in rollers and cylinders, but also to torsional vibrations of cylinders or drums. The latter are propagated via gearwheels of the gearwheel train. The occurring torsional vibrations can be described by a number of characteristic forms and amplitude/time profiles assigned thereto. In this regard, the characteristic forms reproduce a local amplitude distribution. They are printing machine properties independent of the excitation, and they depend upon the number of printing units and upon the type of construction of the machine. Such machine vibrations can be controlled by passive and active accessory systems.
The published European Patent Document EP 0 592 850 B1 discloses a device and a method providing active actuating elements, for example motors, on individual cylinders in order to activate the motors via measurements and controls so that regulating forces for damping the vibrations are generated. This is not an originally targeted counterstrategy against vibrations in the machine-typical characteristic forms, but rather, the vibrations which occur are measured and are thereafter controlled at the measurement location. In this way, compensation is not timely optimized, however, and requires a great outlay for regulating purposes, the risk being that regulation either has too great a time delay or itself causes vibrations. Nor are the compensating measures optimized with regard to the location thereof. If only a single actuating member is provided, it may lie at the zero crossing of a characteristic form of the printing machine, and, at this point, neither a value for the vibration in this characteristic form is determined, nor can countertorques be introduced thereat. If the compensating measure takes place at a location of low amplitudes of the characteristic form, correspondingly higher torques are required. In any case, a great outlay in sensor and regulation technology is required.
It is accordingly an object of the invention to provide a method and a device of the type mentioned in the introduction hereto, namely, for compensating torsional vibrations of a printing machine by introducing torques which compensate the vibration excitation, so that optimum compensation of torsional vibrations of a printing machine is achieved at the least possible expense or outlay.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method for compensating torsional vibrations of a printing machine by introducing torques which compensate vibration excitation, which comprises determining at least one characteristic form of a printing machine for at least one location on a drive train of the printing machine, determining and storing at least one respective countertorque for compensating the torques which excite vibration in a characteristic form at a location whereat the characteristic form is not zero, and applying the at least one countertorque at the corresponding location so that the vibration is maximally reduced due to the application of the at least one countertorque.
In accordance with another mode, the method of the invention includes selecting the location for applying the at least one countertorque thereat because it is a location at which the amplitudes of the vibration in the characteristic form are high.
In accordance with a further mode, the method of the invention includes using a plurality of characteristic forms of a printing machine for determining countertorques.
In accordance with an added mode, the method of the invention includes determining the countertorques for an average rotational speed of the machine.
In accordance with an additional mode, the method of the invention includes determining the countertorques for various rotational speeds of the machine.
In accordance with yet another mode, the method of the invention includes, for changing the phase relationship of the required countertorques, introducing into the drive train at least two partial torques, the phase relationship of which is adjusted correspondingly.
In accordance with yet a further mode, the method of the invention includes, for a printing machine operating in a verso printing mode, determining the countertorques separately for each machine region adjacent to a reversing device, and separately applying the corresponding countertorques for each machine region.
In accordance with another aspect of the invention, there is provided an apparatus for performing a method of compensating torsion vibrations by introducing torques which compensate vibration excitation, comprising at least one device for introducing torques into a drive train of a printing machine for compensating vibration excitations, said at least one device being disposed at a location of the drive train at which a characteristic form having an excitation which is to be compensated is not zero, the torque for compensating the torques which excite vibration in the characteristic form being introducible to said at least one device, and said at least one device being able to impart a countertorque to said drive train.
In accordance with another feature of the invention, the at least one device is disposed at a location on the drive train at which amplitudes of the characteristic form are high.
In accordance with a further feature of the invention, the apparatus includes further devices for applying further countertorques, the further countertorques serving for compensating torques which excite vibration in further characteristic forms.
In accordance with an added feature of the invention, the at least one device is constructed for storing and retrieving countertorques for various machine parameters.
In accordance with an additional feature of the invention, the apparatus is in combination with a printing machine having at least one reversing device, each machine region adjacent the reversing device having the countertorque-applying device assigned thereto.
In accordance with yet another feature of the combination, the printing machine is convertible between recto printing and verso printing mode, and during such a conversion, the countertorque-applying device is adjustable therewith for the machine region adjusted in angular relationship thereof to the rest of the machine, so that the countertorques are applicable in a correct phase relationship.
In accordance with yet a further feature of the combination, the device for introducing torques is a motor.
In accordance with yet an added feature of the combination, the device for introducing torques comprises a hydraulic application of torque.
In accordance with yet an additional feature of the invention, the combination includes a control for receiving an entry therein of countertorques for various rotational speeds of the machine.
In accordance with an alternative feature of the combination, the device for introducing torques is at least one cam mechanism.
In accordance with still another feature of the combination, the cam mechanism has a cam disk fixedly connected to a gearwheel of the drive train, and a roller is included for applying a force to the cam mechanism.
In accordance with still a further feature of the combination, the cam mechanism has a stationary cam disk, and there is included a roller rotatable by an arm connected to a cylinder journal for applying a force to the cam mechanism.
In accordance with still an added feature of the invention, the combination of the invention includes an energy-storing device actable on a lever carrying the roller for applying the force.
In accordance with a concomitant feature of the invention, the combination of the invention includes an equalizing mass actable on the roller.
With regard to the method, the object is achieved in that at least one of the characteristic forms of a printing machine is determined, in that, for at least one location on the drive train of the printing machine, at which location the characteristic form is not zero, the respective countertorque for compensating the torques which excite vibration in the characteristic form is determined and stored, and in that the countertorque is applied at the corresponding location in such a manner that the vibration is maximally reduced as a result of the application of the at least one countertorque.
With regard to the apparatus, the object is achieved in that the at least one device is disposed at a location on the drive train at which the characteristic form is not zero, in that the torque for compensating the torques which excite vibration in the characteristic form is introduced to the at least one device and the at least one device imparts the countertorque to the drive train.
The essence of the invention is that even the origination of vibrations is as far as possible prevented. For this purpose, either the characteristic form having the largest fraction of overall vibration or this and other characteristic forms are determined for a printing machine. Then, for any location on the printing machine, at which location the corresponding characteristic form is not zero, the time profile is determined which a countertorque must have in order to compensate the torques which excite vibration in the characteristic form. This countertorque is then applied in order to prevent vibration excitation from the outset. As a result, excitation to the vibration in one characteristic form can be prevented in a concerted manner, without the vibrations in the remaining characteristic forms becoming excited to an appreciably greater extent. Because the vibration in one characteristic form normally predominates, this usually being the first characteristic form, a marked reduction in the vibrations over the entire length of the printing machine can be achieved by the introduction of countertorques at one location or at a few locations. If vibrations in further characteristic forms are also compensated, under some circumstances amplifications in the vibrations of the other characteristic forms occur, which are likewise to be compensated. The mutual reactions must therefore also be incorporated into the torques for the purpose of compensation. In this case, although the excitations of the characteristic form under consideration have some rotational speed dependence, this dependence is often not so great that it has to be included in the determination of the countertorques in every case. It is therefore often sufficient, in many cases, to determine and apply the countertorque for one or two locations on the printing machine and one rotational speed, in order to achieve effective compensation of the torsional vibrations of the printing machine. A measure of this kind entails a very low outlay. However, even the introduction of countertorques dependent on rotational speed involves a considerably lower outlay than the aforementioned regulation according to the prior art. Regulation and sensor technology are not required in the subject according to the invention.
Expediently, the location selected for applying a countertorque is a location at which the amplitudes of the characteristic form under consideration are high. The devices by which the torques which excite vibrations are compensated from the outset by countertorques is then also arranged at this location on the drive train of the printing machine. The aforementioned expedient refinement is obtained due to the fact that control of the vibrations is not possible at the zero crossing or near the zero crossing. By contrast, at the location of the highest amplitudes of the characteristic form, the vibrations assigned to this characteristic form can be controlled with the least possible outlay in terms of countertorques.
In order to control the torsional vibrations of a printing machine, the characteristic form which has the largest fraction of the overall vibration may be used. Here, this is, as a rule, the first characteristic form. It is also possible, however, to determine a plurality of characteristic forms of a printing machine in order to apply countertorques. In this regard, the countertorques must be calculated or measured correspondingly. Further devices for applying countertorques may, however, also be provided, in which case the countertorques must be determined for each location, taking into account the influence of the countertorques introduced at other locations.
The countertorques depend to some extent upon various parameters. As a rule, however, the influence of these can be ignored and average values can be selected. The rotational speed of the printing machine exerts the greatest influence. On many machines, however, the determination of the countertorques may likewise be performed for an average rotational speed of the machine. It is also possible, however, for the countertorques to be determined and applied for different machine rotational speeds. Other parameters may, however, also be taken into account correspondingly. Besides influences on the intensity of the required countertorques, there are also influences that do not relate to the intensity, but rather, to the phase relationship. This is the case with regard to format adjustments in verso printing or during the conversion or changeover from recto printing to verso printing, or the reverse. Because the phase relationship of the elements causing the vibrations is modified during these changeovers, the phase relationship of the torques exciting the vibration also changes and the phase relationship of the countertorques must therefore also be changed.
Particularly with regard to machines with a reversing or turning device, provision is made, in order to change the phase relationship of the countertorques required, for introducing into the drive train at least two partial torques, the phase relationship of which can be adjusted correspondingly. It is expedient, in a machine of this type, to determine the countertorques separately for each machine region adjacent to a reversing device. This necessitates a corresponding adaptation of the stored countertorque or at least two devices for introducing torques have to be mounted on the drive train, so that the corresponding countertorques are applied separately for each machine region. If installed appropriately, the devices are coadjusted along with cylinder adjustments, and the correct phase relationship is thereby also assigned automatically.
At least two of the devices would have to be provided in the case of one reversing device, at least three of the devices in the case of two reversing devices, and so forth. It is expedient, under these circumstances, that, when the printing machine is converted or changed over, the device for applying the countertorques is coadjusted for the machine region adjusted in the angular relation thereof to the rest of the machine, in such a manner that the countertorques can be applied in the correct phase relationship. The advantage of this is that, with the changeover or conversion from recto printing to verso printing, or the reverse, the devices for applying the countertorques are coadjusted in such a way that they always have the correct setting. For example, when cam mechanisms are mounted on cylinders or drums, coadjustment takes place so that the correct phase relationship of the partial torques for compensation is always set automatically. In a refinement of this type, the correct phase relationship is, as it were, stored mechanically.
The devices for compensating the torques which excite vibration in a characteristic form may be constructed in a wide variety of ways. For example, the device may be a motor or comprise a hydraulic application of torque. A control device is then necessary, wherein the magnitude and/or the phase relationship of the countertorque or countertorques are stored. The filing of a plurality of countertorques and, if appropriate, the phase relationship thereof is necessary when various parameters, for example, various rotational speeds of the printing machine, are to be taken into account. Parameters of this type may, of course, also be various paper formats in verso printing or the aforedescribed changeover or conversion from recto printing to verso printing, or the reverse.
In a particularly simple construction of the device, the latter is at least one cam mechanism. Such cam mechanisms can be constructed in various ways.
According to one proposal for the construction as a cam mechanism, a cam disk is provided, which is connected fixedly to a gearwheel of the drive train and which is loaded with a force by a roller. Conversely, of course, the cam disk may also be stationary and the roller mounting be connected fixedly to a gearwheel. In this case, loading with force may be carried out by an energy store, for example, a spring-loaded lever. By virtue of this simple construction, the required countertorque is applied independently of the rotational speed of the machine. This, in many cases, is already sufficient and leads to good results. If there is provision for an equalizing mass to act additionally on the roller, torque loading dependent upon the rotational speed is achieved as a result of the inertia of the equalizing mass. Force loading may also be performed by a double lever which is mounted on the gearwheel or on an arm connected to the latter and carries at one end the roller and at the other end an equalizing mass.
The two measures mentioned above may be combined with one another, in that both an energy storage device and an equalizing mass act upon the roller lever. A device for applying countertorques is thereby obtained, which first applies a partial countertorque independently of the rotational speed and, with an increasing rotational speed, provides an additional partial countertorque which takes into account the variation in the necessary countertorque when the machine is running at a higher rotational speed. The countertorques for different rotational speeds of the machine can thereby be, as it were, stored mechanically in a very simple manner.
Proposals made for implementing the principal according to the invention are, of course, only an illustrative list, and a multiplicity of possibilities for filing the necessary countertorques in terms of magnitude and phase relationship and also for applying the countertorques, even in the form of a plurality of partial torques, are possible.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and apparatus for compensating torsional vibrations of a printing machine by introducing torques which compensate the vibration excitation, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.